I you want hot ice that is safe to put body parts in (like your hand), you want to use a vinegar and baking soda mixture. Boil until solids begin to precipitate and shake the mixture to further saturate. Wait until the mixture cools and starts to form crystals. Save some of the crystals (as they will be needed to initiate the reaction) and clean out the rest using rubbing alcohol and straining the alcohol out of the crystals. Melt the crystals in the microwave until they form a liquid. This is your supersaturated Sodium Acetate Trihydrate mixture. Let it chill in the fridge for about 10-15 minutes. Then, put the crystals you saved on a piece of tin foil. Pour the mixture over it and the same reaction will occurr, but this time it will be much less hot and you will be able to touch it.